The FBI has reportedly told various police departments throughout the U.S. to keep their use of “stingray” cellphone trackers quiet and to not inform the public of their use.

A “stingray” is a cellphone signal interception device which, according to the Daily Caller, may appear to citizens as regular cellphone towers. These trackers trick cellphones and similar devices into connecting with the tracker and once connected, whoever controls the “stingray” can access the device’s call records, texts, location, and other metadata.

Originally, the trackers were developed by the Harris Corporation for use in anti-terrorism operations throughout the U.S. in conjunction with the FBI. However, these trackers have been reportedly used in routine police work in recent years, often without a warrant. The Harris Corporation and FBI have remained silent about the full extent of the technology’s capabilities.

In order to keep the technology’s capabilities quiet, the U.S. marshals have been sent to seize physical documentation from a Florida police station which reportedly detailed the use of the trackers by the police department.

FK – Funny how they don’t get the concept that they work for us…